The process of adsorption of biological species to solid supports finds a number of practical applications in purification, detection and removal of target molecules from multicomponent streams. For example, ion exchange, hydrophobic and affinity ligands are able to adsorb many agents preferentially to chromatographic supports to affect their separation from aqueous solutions. Once adsorbed, the biological agent can either be eluted as a product, or detected by ELISA and other analytical approaches.
In some instances, the solution containing the target biological agent also contains large entities such as red blood cells, viruses, bacteria, liposomes, leukocytes, and aggregates of various sizes. In many of these instances, it is desirable to allow the large aggregates to flow through the solid matrix or support without interfering with the ability of the target biological agents to bind to the support. This requires pore spaces in the solid matrix that are large enough to accommodate the flow of the large entities. Unfortunately, large pore spaces can have a low surface area that limits the capacity of the solid matrix to bind to the target agents.
In other cases, it is desirable to actually filter the large particles to facilitate adsorptive separation of the smaller target agents. One example is the removal of cells from a culture medium to recover an extracellular product.
In addition, there are many instances where it is desirable to bind, rather than filter, the biological entities that are very large. For example, it is of importance to adsorb specifically many pathogens, including infectious prions, viruses, bacteria, and toxins from mixtures of biological agents. These entities often have difficulty accessing the small pores that are required for binding in the currently available sample purification and separation devices.
Nonwoven fibers or webs, also referred to as melt blown polymer fibers or spunbonded webs, are well known and are used for filtration and separation of fine particles from air and aqueous solutions. (see, for example, U.S. Pat. Nos. 4,011,067 and 4,604,203, each of which is incorporated herein by reference in its entirety). Loading of sorptive particulates in nonwoven webs is also well known in the art (see, for example, U.S. Pat. Nos. 4,433,024; 4,797,318; and 4,957,943, each of which is incorporated herein by reference in its entirety). Applications include face respirators for removing particulates and gaseous contaminants, protective garments, fluid retaining articles, and wipers for oil.
More recently, methods for the fabrication of particle impregnated nonwoven fabrics for separation and purification have been reported. See, for example, U.S. Pat. No. 5,328,758, incorporated herein by reference in its entirety. The patent teaches functionalized particles for the attachment of affinity ligands. It is disclosed that the particles are blown into the polymer fibers during the melt blowing stage. The nonwoven fabric comprises pores having pore sizes in the range of 0.24 to 10 μm, preferably 0.5 to 5 μm. It is also specified that the impregnated fabric material must have a Gurley Time of at least 2 seconds.
WO93/01880 discloses a leukocyte-removing nonwoven fabric filter material produced by dispersing in a medium a mass of a great number of small fiber pieces having a fiber diameter of not more than 0.01 μm and a length of about 1 to 50 μm, together with spinable and weavable short fibers having an average length of 3 to 15 mm. U.S. Pat. Nos. 4,550,123 and 4,342,811, each of which is incorporated herein by reference in its entirety, describes microporous polymeric fibers and films which contain particles capable of sorbing vapors, liquids, and solutes. Typical sorbent particles include active carbon, silica gel, and molecular filter type materials.
The invention as disclosed herein provides devices and methods for sample purification, and detection and removal of target agents from a sample with increased efficiency and specificity and substantial savings in time and cost over the devices of the prior art.